A method and efficient numerical algorithms of solving the problem of diffraction of electromagnetic waves on a multi-layer spherically symmetric structure, excited by a generalized Huygens, are considered. It is shown that the method is based on reducting the source vector problem to two scalar problems for Debye potentials. The amplifying ration and directional diagrams of antennas based on spherical dielectric lenses are researched and experimental estimation of numerical results is given.